Abstract
DFT with a Hubbard-U method was utilized to elucidate oxygen vacancy formation and migration in lanthanum strontium ferrite (LSF) at different La:Sr ratios (∞, 1, and 0) and oxygen non-stoichiometries (0-0.5). With alteration of the La:Sr ratio, it was found that the oxygen vacancy formation energy varies by ~ 3 eV but the oxygen vacancy migration barrier only varies by ~ 0.5 eV. The Fe oxidation state controls the ease of oxygen vacancy formation, as well as the size and shape of the oxygen vacancy polarons; which, in turn, play the principal role in determining the amount of oxygen vacancy interactions in LSF. Even though these oxygen vacancy interactions are responsible for phase changes which dramatically alter the oxygen vacancy formation energy, the oxygen vacancy polarons (and hence the amount of oxygen vacancy interactions) and the LSF crystal structure have little effect on the oxygen migration barrier.
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